As integrated circuit (IC) and system designs are getting more complex, so do the supply current requirements. To handle such requirements, high current switch mode power supply (SMPS) designs are typically used. The SMPS is very often integrated into the same die as sensitive analog circuitry. While the SMPS greatly benefits the power dissipation of the device, the high current switching can also induce unwanted noise that can be detrimental to normal operation of sensitive circuits, both on and off the IC, as well as radiated and conducted emissions produced by the SMPS.
Thus, in systems using a highly specialized application specific integrated circuit (ASIC) and where such high current is not required, it is generally advantageous to use a standard linear Regulator instead of using the high current SMPS topology. While using the standard linear Regulator increases the power dissipation, it also greatly reduces the noise induced from the high frequency switching of the SMPS topology. Further, it is desirable to use the same power supply for both high and low power applications.
One current technique that uses the power supply for both the low and high power applications requires programming the Regulator circuit during a final test, which could be via a fuse, EEPROM, or a metal mask change. Another current technique that uses the same power supply for both the low and high power applications requires an additional external pin in the Regulator topology to facilitate selection of the desire mode. All of these solutions either require separate part numbers for the EEPROM, fuse, or a different IC for the metal mask change solution. The use of an external pin for selection of low and high power applications may not be an option available, especially when the IC package is pin limited. Additionally, if the IC package/pin out needs to be backwards compatible with previous revisions, an addition of a pin and/or a change in the PCB layout may be may not be feasible or desirable.